Chicken Pot Pie Soup

Name: Chicken Pot Pie Soup
Ingredients: 3 Tbsp. unsalted butter; 3 Tbsp. all-purpose flour; 3 large shallots, coarsely chopped; 2 medium carrots, peeled, coarsely chopped; 2 celery stalks, thinly sliced; 2 tsp. Diamond Crystal or 1 tsp. Morton kosher salt, divided, plus more; 3 garlic cloves, thinly sliced; 2 tsp. thyme leaves; Freshly ground pepper; 1 cup dry white wine; 1 lb. small potatoes, scrubbed, cut into ½ pieces; 7 cups low-sodium chicken broth; 2 Tbsp. Dijon mustard; 1 sheet frozen puff pastry (one 14-oz. package or half of a 17.3-oz. package), thawed; 1 large egg, beaten to blend; Flaky sea salt; 2 cups shredded cooked chicken meat; 1 cup heavy cream; ½ cup frozen peas; Chopped parsley (for serving)